The present invention relates to a magnetic filtration system for filtering ferrous and some non-ferrous material from a fluid in which said material is in suspension.
The magnetic filter device of a previous application (9515352.4) (WO97/04873) (MARLOWE) comprises an annular magnet disposed between a pair of annular metal plates. Fluid flows into the device through recesses in the metal plates, and returns through the centre of the device when used in conjunction with a conventional filter.
Another device (FREI) (U.S. Pat. No. 2,149,764) uses a series of cylindrical magnets separated by a series of metal baffle plates, which are magnetised through contact with the magnets. The flux fields generated are designed to collect particles on the plates themselves and also around the edges of the perforations in the plates. A metal screen abuts the edges of the plates and is therefore magnetised through contact with it. The screen forms an envelope around the arrangement and is designed to increase the magnetised area in the actual flow path. Disadvantageously, however, the metal particles, which build up on the screen, form an ever-increasing obstruction to flow. In addition, any particles collected on the plates are exposed to the flow, and are in danger of being washed off. In the present invention, the magnetic flux direction and properties are used to advantage as described later herein.
A magnetic filtration system for filtering ferrous and some non-ferrous material from fluid, in which said material is in suspension, comprises inlet and outlet means. The system can advantageously be inserted at almost any point in a fluid system. The filtration system comprises one or a plurality of collection units that can be disposed in a housing. Magnetisable material, in particular ferrous particles and some non-ferrous particles drawn along with the ferrous particles can be collected in the collection units. Particles are advantageously magnetically held out of the flow path, and therefore do not result in obstruction of flow. The collection units can be readily removed from the housing, to be dismantled, cleaned of any material collected and re-installed for re-use in the system. In an embodiment where the magnet is an electromagnet, when the electromagnet is active, material can be collected from the fluid, and when the electromagnet is deactivated, the material collected can be removed from the units and disposed from the system.
The present invention is applicable to fluid systems that are subject to high flow rate and pressure.
In accordance with one aspect of the present invention, there is provided a magnetic filtration system for filtering magnetisable material from a fluid in which said material is in suspension comprising inlet means and outlet means, in which one or a plurality of collection units is disposed, each collection unit comprising one or a plurality of plates or plate arrays disposed either side of one or a plurality of magnets so that the plates or plate arrays have opposing polarities, wherein portions of the plates or plate arrays extend beyond part or all of an edge or edges of one or a plurality of said magnets, facing plates have one or a plurality of apertures, and wherein facing apertures define a region of magnetic repulsion, and facing plate portions define therebetween, a region of magnetic attraction and magnetisable material collection, such that the magnetic flux fields thus created facilitate preferential collection of magnetisable materials in the collection region between facing portions rather than in the region between said facing apertures.
It is an advantage that the facing collecting regions alternate with facing apertures such that the attractive flux fields generated in the collection regions and the repulsive fields disposed either side thereof facilitate collection in a volume sandwiched between exposed facing plate portions. Particles can thus be retained in three-dimensional space rather than on merely the magnetised surface area that is exposed to fluid flow. Each collection unit thus offers greater capacity for debris than that possible with the exposed surface area of its component parts when disassembled. The repulsive forces in the apertures of each collection unit divert magnetisable material from the apertures so that they collect preferentially between facing plate portions rather than in the apertures, to thus allow fluid to continue to flow through the unit even at capacity.
Advantageously, the respective plates of adjacent collection units having like polarity are disposed adjacent to one another so as to substantially restrict the collection of magnetisable particles to the collection regions substantially within the interior of the collection units. An individual collection unit will have its own distribution of magnetic flux, part of which are regions of magnetic attraction between the facing plate portions of the unit. If another unit is disposed so that the respective neighbouring plates have unlike polarity, one North, the other, South, the flux existent within the collection unit (as an individual) will be dispersed through the generation of further magnetic fields of attraction between adjacent collection units. If the collection unit is disposed beside another so that like poles of adjacent plates are facing, then the repulsive forces thus created between adjacent collection units will condense the attractive magnetic flux towards the region between facing plate portions, more so than when there are no further adjacent units.
Advantageously, there is provided a housing made of a non-magnetisable material. This limits magnetisable material collection to the collecting regions within the collection units if the collection units are disposed in close proximity to the interior of said housing. The housing can be made of a magnetisable material if said collection units still facilitate fluid passage therethrough even when filled with contaminant.
It is an advantage that there is provided a housing integral to a fluid flow system, said filtration system still permitting fluid flow the through even at capacity.
In one embodiment, each collection unit can be further separated from an adjacent collection unit by a spacing member. This allows for the better utilisation of the available magnetic flux density.
It is an advantage that the spacing member is non-magnetic. It is also an advantage in certain instances that the spacing member is magnetic. The magnetisation or non-magnetisation of the spacing member is discussed later.
It is an advantage that the apertures in respective collection units, which are in closer proximity to the inlet means, are larger than those of units disposed nearer the outlet means. This provides collection units of varying magnetic strength along the direction of flow and alleviates any collection bias on the collection units closest to the inlet.
It is preferred that alignment means is provided for disposing the apertures and plate portions in facing plates of a collection unit in substantial axial alignment. As fluid flows more smoothly through apertures that are aligned, regions of particle collection surrounding the apertures are thus exposed to a minimum of fluid turbulence, thus aiding in the retention of material collected. The presence of an aperture on a plate creates adjacent plate regions of like polarity, which thus generate between them, an axial region of magnetic repulsion. By aligning a pair of apertures of facing plates, the region of magnetic repulsion extends through an axial length of the collection unit. As the apertures are also the means for fluid flow through the collection unit, the path of fluid flow is also the region from which magnetisable particles, suspended in the fluid, will be repelled. As the repulsive force acts radially, particles will tend to be redirected from the fluid flow path and repelled towards the adjacent region between the plate portions either side of the axial region of repulsion. The plate portions have between them, an attractive magnetic force acting substantially orthogonally to that of the repulsive flux field. Particles entering the axial recess between facing apertures are thus both repelled from the axial recess and attracted towards the attractive flux field of the gap or collecting region. Furthermore, as each collecting region has apertures either side of it, the attractive flux lines in the collecting region are further condensed by the repulsive flux lines extending orthogonally on either side. Condensing the flux lines increases the magnetic field strength in that region. It is the combined actions of these two fields that enables the apertures to be kept free of magnetisable particles and that enables particles to be held in the collecting region despite high fluid flow (for example 400 liters/minute) and fluid pressure (for example 7000 psi).
It is an advantage that further alignment means is provided for disposing the apertures of respective collection units in substantial axial alignment. This too will minimise the fluid turbulence between collection units, to any particles held magnetically in respective collection units.
Advantageously, said alignment means and further alignment means comprise a tab of given dimension on an internal edge of the plate and an axial unit having a groove of corresponding dimension to that of the tab, into which groove said tab can locate to provide a chosen axial and radial alignment of the facing plate portions and apertures of a collection unit and/or those of an assembly of collection units.
Preferably, the magnetic filtration system is further provided with flow directing means for directing fluid flow from the inlet means towards the apertures in said plates. The internal surface of the housing of the filtration system can be contoured into a conical shape and the upper portion of the axial unit provided with a conical portion so that fluid from said inlet means is radially dispersed towards the apertures in the more or most proximal collection unit. Alternatively, a unit separate from the housing and the axial unit may be included between the inlet means and the first collection unit, with an annular conical channel for directing fluid flow in the same manner.
Preferably, further slot-like apertures are provided in facing apertures and facing plate portions to further enhance the magnetic flux density between the facing plates of each collection unit. The provision of slot-like apertures, which are aligned in facing plate portions, creates regions of magnetic repulsion, which are closer together than those of the first-mentioned apertures. The closer like poles are disposed to one another, the more intense the forces of magnetic repulsion between them will be. The inclusion of such regions, for instance, in the middle of a collecting region further focuses the attractive flux fields in these regions. The repulsive magnetic forces acting radially further condense the flux density of the attractive flux lines, between facing plate portions, acting axially.
Advantageously, facing pole piece pairs are curved towards one another to further enhance the magnetic flux fields therebetween. As one pole piece is magnetised North and the other, South, the closer they are disposed to one another, the stronger the flux between them will be, up until a point where the plates are saturated with magnetic flux from the magnet. In addition, as flux is dispersed through the edges of the plates, curving the edges of facing pole pieces towards each other redirects the flux to an axial region between the plates. If the plates are left uncurved, the flux fields will extend radially from the edge of the plate. A field of attraction will still be generated between facing pole pieces, but of lesser strength than where they are curved towards one another, where the flux fields emerging from facing pole pieces are substantially directed towards one another.
Advantageously, facing plates/plate arrays are separated by a distance which best utilises the magnetic flux emergent from the edges of said facing plates to attract and retain magnetisable material in the fluid and which also provides the collection capacity required. The larger the collection capacity of the unit, the less frequently it will need cleaning. Thus the separation of the plates can be varied to determine the required capacity for material as well as the magnetic flux intensity distributions in the collecting regions and in the apertures. The plates are brought together in close enough proximity to enable axial collection, in the collecting region between the internal portions of each plate pair, of magnetisable particles, as small as one micron in size, despite high fluid flow (for example 400 liters/minute) and high pressure (for example, up to 7000 psi).
Advantageously, that the attractive flux lines between facing plate portions are substantially orthogonal to the repulsive flux lines in the apertures, such that magnetisable material entering the apertures, is subject to the influence of both attractive and repulsive flux fields.
Advantageously, internal surfaces of the housing are disposed in close proximity to the outer portions of the plate/plate array pairs in order to substantially constrain fluid flow in the filtration system to regions in which magnetic flux fields generated by plate/plate array pairs facilitate the attraction and retention of the size range and type or types of non-magnetisable particle input to the filtration system, for example, ferrous particles smaller than one micron.
Alternatively, where the housing is substantially larger than the diameter of the plates, the clearance between the collection units and the housing may encompass regions beyond the efficient magnetic range of the collecting region. In such an instance, it is preferable to include one or a plurality of distribution plates having further apertures in substantial axial alignment with said plate apertures, which can be disposed either side of one or more of the collection units to ensure that all fluid is exposed to regions having magnetic flux density, similar to, or greater than a threshold required for particle attraction. The different sizes of particle and the type of particle in suspension in the fluid will have different such thresholds. These threshold intensities also depend on the size and type of other material in suspension as well as fluid flow and pressure. For instance, the threshold intensity required to attract a particle which of a given size, for example 1 micron, will rise if other forces acting on the particle are increased, as when fluid pressure is increased or if fluid flow is increased.
Preferably, the housing comprises one or a plurality of sealable sections with interlockable threaded portions that enable said sections to be readily assembled or dismantled. The sections of the housing screw apart to facilitate insertion or removal of the collection unit assembly into or from the housing, and screw together to encase the assembly. When required, the assembly can be removed from the housing, cleaned of any magnetisable material debris present and replaced inside for re-use.
Preferably, the housing is further provided with means for attachment to a fluid system.
Advantageously, isolation means may be provided for isolating (blanking off) fluid flow to and from the filtration system to facilitate its removal from and insertion into the fluid system.
Advantageously, monitoring means for monitoring the presence and/or amount of material collected is disposed in the filtration system, so that particle collection and therefore wear can be assessed without dismantling the system.
It is preferred that close down means is provided for enabling a system, of which said filtration system is a part, to be closed down if a pre-determined level of debris collected is reached. If the wear of a component can be assessed at an early stage, other components sharing the same fluid will be less likely to wear and complete system failure, perhaps involving substantially accelerated wear of several components and/or mechanical seizure, is thus less likely.
Advantageously, conventional filter media is disposed in the housing to remove non-magnetisable particles input to the system.
Advantageously, the magnet or magnets in the collection unit(s) is/are electromagnet(s) having switch means for activating the electromagnet(s) to collect particles and for de-activating the electromagnet(s) to facilitate release of any particles collected. This will facilitate more convenient removal of any material accrued in the collection unit before its re-use. The switch means, disposed outside the housing for manual access, is used to activate or de-activate the electromagnet depending on whether the collection unit is in a filtration mode or in a cleaning mode. Alternatively, the switch means can be disposed inside the housing if external remote means of its operation are provided.
A further advantage of the present invention resides in the fact that the magnetic elements can impart some magnetism to the fluid flowing therethrough and this can be used in a manner well known to those skilled in the art and therefore not described in more detail herein.
It is preferred that conventional cellulose fibre, metal or other filter material is disposed in the magnetic filtration system to remove non-magnetisable material input to said system. Advantageously, the filter material is placed downstream of one or a plurality of collection units.
In accordance with a further aspect of the present invention a method of operating a system for the removal of magnetisable particles from a fluid system in which said particles are in suspension, includes providing an apparatus comprising inlet means and outlet means, in which one or a plurality of collection units is disposed, each collection unit comprising one or a plurality of plates or plate arrays disposed either side of one or a plurality of magnets so that the plates or plate arrays have opposing polarities, wherein portions of the plates or plate arrays extend beyond part or all of an edge or edges of one or a plurality of said magnets, facing plates have one or a plurality of apertures, and wherein facing apertures define a region of magnetic repulsion, and facing plate portions define therebetween, a region of magnetic attraction and magnetisable material collection, passing fluid through said apertures, retaining said particles in said regions of magnetic attraction and repelling particles from said apertures.
Advantageously, said method of operating the system includes the steps of detaching the plates from the magnets and then wiping off debris from the plates and the magnet, or alternatively, blowing the debris off the undismantled collection unit assembly with an air line. Particles are easier to blow off if the air line is directed across the flux lines of attraction rather than parallel to them.
In accordance with a still further aspect of the present invention, a method of operating a system for the removal of magnetisable particles from a fluid system in which said particles are in suspension, includes the steps of providing an apparatus comprising inlet means and outlet means, in which one or a plurality of collection units is disposed, each collection unit comprising one or a plurality of plates or plate arrays disposed either side of one or a plurality of electromagnets so that the plates or plate arrays have opposing polarities, wherein portions of the plates or plate arrays extend beyond part or all of an edge or edges of one or a plurality of said magnets, facing plates have one or a plurality of apertures in axial alignment, and wherein facing apertures define a region of magnetic repulsion, and facing plate portions define therebetween, a region of magnetic attraction and magnetisable material collection, passing fluid through said apertures, activating the electromagnet to retain said particles in said regions of magnetic attraction and repel particles from said apertures, de-activating the electromagnet to release the particles from said regions of magnetic attraction and disposing of said particles from said fluid system.
Advantageously, the method for activating and de-activating the electromagnet includes passing current through coils of the electromagnet.
Advantageously, monitoring the quantity and/or type of debris collected includes the steps of providing detection means for detecting the presence of particles collected between facing plate portions, part of which detection means extends in the collecting region of one or more collection units, monitoring the type or quantity of material present, providing alarm means, setting off the alarm if material quantity rises beyond a pre-determined rate or amount, providing closing down means for the fluid system and closing down the fluid system if the quantity of material rises beyond a further pre-determined rate or amount.